Living in public rental housing is healthier than private rental housing a 9-year cohort study from Japan Gerontological Evaluation Study

Housing tenure is an important aspect to determine health. However, even though renters tend to have more socioeconomic disadvantages than homeowners, mortality risk between private and public renters compared with homeowners remains unclear. Japanese public rented housing, such as the Urban Renaissance Agency, has been developed for supplying an adequate living environment since 1950s. This study aimed to examine the mortality risk among older Japanese residents living in private and public rented houses compared with those living in owner-occupied houses using 9-year follow-up data. This study drew upon a 9-year follow-up of participants in the Japan Gerontological Evaluation Study, a population-based cohort study of Japanese independent adults aged ≥ 65 years. Mortality from 2010 to 2019 was analyzed for 44,007 respondents. Housing tenure was defined by a questionnaire. Cox regression models were used for calculating the hazard ratio for mortality. Bonferroni correction was used to account for multiple testing between rental houses. Overall, 10,638 deaths occurred during the follow-up period. Compared with housing owners, all rental housing groups had a significantly higher risk of mortality. Among renters, participants who lived in public rental housing had the lowest risk of mortality even after adjusting for sociodemographic characteristics, health status, social status, and environmental status. Multiple testing among renters with Bonferroni correction showed that public renters had 0.80 times (95% CI 0.72–0.89) lower mortality risk than private renters. Although Japanese older adults living in public rental housing had a higher mortality risk than homeowners, this risk was lower than that among private renters. A positive neighborhood environment based on well-planned urban development may have contributed to this result. The results suggest that planned urban development lowers the risk of mortality in older renters in Japan.

money or renewal fees) and guarantor requirements common in private rentals in Japan.Public housing developed by the UR refers to the implementation of Perry's Neighborhood Unit Theory, which involves the deliberate placement of open spaces, commercial facilities, public facilities, and internal streets 25 (Fig. 1).According to the Ministry of Land, Infrastructure, Transport and Tourism's 2022 housing economic data, the total number of housing in Japan was 53,616,300, of which 1,922,300 were public rental housing and 747,200 were UR apartments.Furthermore, another report from the Ministry of Land Infrastructure Transport and Tourism showed the distribution of rental housing managed by the UR throughout Japan.According to the report, as of 2012, of all apartment complexes (1732 apartment complexes) managed by the UR, the total for Tokyo, Kanagawa, Chiba, Saitama, and Ibaraki was 911 (52.6%).Furthermore, 124 (7.2%) complexes were located in the Aichi Prefecture; 422 (24.4%) in Osaka, Hyogo, Kyoto, and Nara; 162 (9.4%) in Fukuoka; and 113 (6.5%) in others 26,27 .These data also showed that public housing operated by the UR was concentrated in urban or suburban areas.The average size of UR houses is 46.6-51.9m 228 .Moreover, as of March 31, 2015, the company announced that it had built 2029 apartment complexes with 883,038 apartments 29 .Based on this data, it has been estimated that each apartment complex has approximately 435 apartments.Several application requirements for UR apartments have been established, such as income requirements and visa (for foreign residents) 30 .The income criterion dictates that the applicant must have an income of four times the rent, thus indicating that not necessarily only low-income families reside in the area 30 .
Public rental housing, such as the UR in Japan, is often larger than private rental housing and is built under planned urban development.If differences in health effects are found between the two, this could clarify some conditions for age-friendly housing.A previous study also revealed that the definition of housing tenure may differ by contextual features, such as historical period, society or region, and culture 7 .Thus, further studies on this topic with different populations and locations are needed.Therefore, this study aimed to examine the risk of mortality among older Japanese residents living in private and public rental houses compared with those living in owner-occupied houses using large-scale 9-year follow-up data.We hypothesized that those who lived in owned houses had the lowest risk of mortality and those who lived in public rental houses had a lower risk of mortality than those who lived in private rental houses.By examining the association between housing tenure and mortality among Japanese older adults, this study can be expected to contribute to creating pieces of evidence for urban planning for healthy older adults.

Figure 1.
Example of a large public housing complex (including the participants of this analysis): Naruko Housing Complex in Midori Ward, Nagoya City, Aichi Prefecture.The area within the dashed lines is the Naruko Housing Complex.The complex was completed in 1964, with many residential buildings being fivestory tall.The main street, which curves to match the terrain, serves as the axis for the area, with a primary school, park, shops, banks, post office, and other facilities located in the center of the complex.The complex also features abundant open spaces with lush greenery between the residential buildings, reflecting the influence of the theory of "the neighboring unit." During its development, 2196 apartments were built and the planned population was approximately 8000 individuals.Aerial photographs were provided by the Geospatial Information Authority of Japan in 2007.

Mortality outcome
The vital status during the follow-up period from 2010 to 2019 (mean: 3087 days; range: 8-3775 days) was determined by linking data of the self-administered questionnaire to mortality records in the longterm care insurance database.In total, 10,638 deaths occurred in the analytical sample (cumulative mortality = 10,638/44,007; 24.2%).This study examined all-cause mortality instead of cause-specific mortality because death certificate data were unavailable.

Housing tenure
Housing tenure was defined using a questionnaire.The participants were asked "What type of residence do you live in?" and answers were (1) Owned house; (2) Private rental house; (3) Public rental house; (4) Company housing or dormitories, and (5) Others.Because the participants who answered "living in company housing or dormitories" were few (n = 87), we combined answers ( 4) and ( 5) to form the "Others" group.Then, we used these four categories in the analysis.

Statistical analysis
Descriptive analysis was performed to summarize the characteristics of the participants.Furthermore, owing to the lack of some variables in this analysis, multiple imputations were performed.Twenty multiple imputed datasets, including all measurement variables, were created using the multivariate normal imputation method under a "missing at random" assumption, after which the estimated parameters were combined using Rubin's combination methods.Cox proportional-hazards model was performed to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality.We have set three models after the crude.In Model 1, sociodemographic factors (sex, age, marital status, educational attainment, equivalent income, living status, longest job held, and employment status) were added.In Model 2, health status (GDS score, hypertension, stroke, diabetes mellitus, hearing disorder, and BMI) was added.In Model 3, social status (social participation in sports and hobby groups, and social support) was added.In Model 4, environment status (population density and duration of residence) was added.Bonferroni correction was used to account for post hoc multiple testing other than owned house, which is private rental house versus public rental house, private rental house versus others, and public rental house versus others.All statistical analyses were performed using Stata 16/IC (StataCorp, College Station, TX, USA).

Ethics approval
This study was reviewed and approved by the Ethics Committee of Chiba University (3442) and the Research Ethics Committee involving Human Participants of Nihon Fukushi University (10-05).The study was conducted according to the principles of the Declaration of Helsinki and its later amendments.The JAGES participants were informed that participation in the study was voluntary, and the completion and return of the questionnaire by mail constituted consent to participate in the study.All participants provided written informed consent when they returned a questionnaire.

Results
Table 1 shows the characteristics of the 44,007 respondents.Of all participants, 37,761 were living in owned houses, 2280 were living in private rental houses, 2490 were living in public rental houses, and 569 were others.Furthermore, the number of participants whose income was low was similar in public rental housing (56.3%) and private rental housing (61.5%), whereas they were higher than participants living in owned houses (38.6%).Moreover, the percentage of participants living alone was also similar in public rental housing (32.1%) and private rental housing (28.6%).Table 2 presents the HRs with 95% CIs for the association between housing tenure and the risk of mortality.After adjusting for potential confounders in Model 4, participants who lived in private rental houses had 1.45 times (95% CI 1.34-158) higher, those who lived in public rental houses had 1.17 times (95% CI 1.07-1.27)higher, and those who lived in others had 1.21 times (95% CI 1.05-1.40)higher risk of mortality than those who lived in owned houses.The results of post hoc multiple testing among non-home owners indicated a significant difference between private and public renters.Public renters have 0.80 times (95% CI 0.72-0.89)lower risk of mortality than private renters (p = 0.0001).The results from other post hoc multiple testing did not indicate significant differences.

Discussion
To the best of our knowledge, this was the first study to investigate the association between housing tenure particularly between residents living in private and public rental housing and mortality risk with four different models.We found that the risk of mortality was the lowest among older adults living in owned houses.Furthermore, the mortality risk was lower in those living in public rental houses than in those living in other types of rental houses.
In this study, even after adjusting for SES, older adults living in owned houses had the lowest risk of mortality.One of the reasons could be that SES is not fully adjusted.Educational attainment, income, and employment status were added as SES in this analysis; however, we did not add other attributes that older individuals may have, such as wealth.Another example of a possible effect from not fully adjusted SES could be the ability to maintain the quality of house.For instance, individuals with higher SES can easily maintain room temperature.In their housing and health guidelines, the World Health Organization strongly recommends controlling indoor cold and heat 41 .Room temperature should be well-balanced indoor temperature to protect health during cold seasons in countries with cold seasons, such as Japan.Older adults with high SES possibly have more capacity to maintain room temperature through, for instance, renovations to maintain room temperature, purchasing a heater or air conditioner, and constantly paying utility bills.
Possibility of a lower risk of mortality among participants living in public rental housing compared with private rental housing is a richer neighborhood environment around public housing that can enhance physical activities and social participation 42 .In Japan, a quantitative supply of houses after World War II 28 enabled a planned design of the surrounding environment around public rental housing, such as parks, sidewalks, and greenery.Having places suitable for exercise in the community has been associated with a lower risk of heart disease in older men 43 .One of the previous studies revealed that people who are living in a social rented dwelling setup were more likely to be exposed to environmental factors that negatively affect their health, such as noise, crime, and vandalism 7 .The study discusses the issue of low availability of health-promoting environments, such as gardens and community amenities.Another study revealed that lower frailty of older adults was also associated with the accessibility of parks and sidewalks 44 .Lack of grocery stores in the neighborhood increases the risk of death, dementia, and need for long-term care and reduces fresh food intake 32,35,45,46 .Moreover, living in a neighborhood with a higher rate of sidewalk installation was associated with a low risk of dementia in urban areas 47 .Another study revealed that living in a higher subjective neighborhood walkability is associated Vol:.( 1234567890 48 .Hence, living in a positive neighborhood environment, which promotes healthy behaviors, may be associated with a lower risk of mortality.Another possible mechanism is the positive effect from well-planned environments, such as greenspaces.As previously mentioned, Japanese public houses are well-developed such that all necessities, including green areas, are distributed around the residence 28 .A cross-sectional study by Nishigaki et al. on 126,878 older adults in Japan revealed that living in greener neighborhoods was shown to be associated with lower risk of depression in urban areas.This could be due to the fact that green spaces in an artificial environment may enhance their impression according to the Attention Restoration Theory 49 .Furthermore, the effect of greenness supports reducing the heat island phenomenon, mitigating noise, or improving the air quality 50 .The health benefits of green spaces are also summarized in the meta-analysis 51 . Moreover, the social dimension may also be a key factor, such as social cohesion.In this study, we added social status (i.e., social participation and support) in Model 3, and the HR decreased by 0.02 after adjusting for www.nature.com/scientificreports/social status.A study showed that owning a home is seen as having achieved the "American Dream" and may contribute to maintaining a high subjective sense of well-being 52 .Living in a Koudan house represented the "Japanese dream" during the rapid economic growth period (during the 1950s and 1970s) in Japan 28 .Because some individuals continue to live in public houses since their working age, they may have stronger social cohesion or networks than those living in other housing tenures.In some studies, it has been reported that social cohesion increases subjective well-being and reduces the risks of all-cause and cause-specific mortality 53,54 .Moreover, Nishina and Oh 55 studied 897 older adults in Japan using cross-sectional data and showed that older adults who live in public housing have more social life variety than those living in owned houses.While private rental houses in this study may contain various characteristics, such as building age (new to old) and accessibility to necessities for life (located convenient area to inconvenient area), Japanese public rental houses may have homogeneous characteristics, such as location or access to necessities.Hence, stronger social cohesion may be a reason for our results.Key strengths of this study were its novelty that the association between housing tenure and the risk of mortality was investigated using cohort data and that participants living in private and public rented houses were compared.Several limitations should be mentioned.First, our analysis was limited to all-cause mortality.Future studies should examine cause-specific mortality to investigate the association between housing tenure and mortality in more detail to determine the impact of environment, such as neighborhood walkability and cardiovascular death.Second, we did not account for the quality of houses.The US Department of Housing and Urban Development outlines eight things to maintain a healthy home: Keep it dry, clean, safe, well-ventilated, pest-free, contaminant-free, well-maintained, and thermally controlled 56 .Japanese old houses tend to be ill thermally controlled, and insulation is inadequate even though it has been stated as a strong recommendation in the housing and health guidelines by the World Health Organization 41 .Japanese census reveals that 59.5% of houses in Japan were built before 2000 57 .Third, we have not analyzed the mechanism of the association; therefore, this association must be further examined.Future analysis should be conducted using data designed to elucidate these issues.Fourth, we have not included the designs of rental housing.It can be imagined that some buildings are designed to promote social interaction in both private and public rental housing complexes; however, such considerations were not considered in this analysis.Fifth, it was impossible to distinguish whether public housing is operated by the local government or the UR.However, according to our JAGES 2019 survey data that allowed us to distinguish them, 55.3% of residents lived in buildings operated by the UR, 33.2% did not, and 11.5% of the data were missing.Sixth, selection bias may be present for residents who want to live in houses operated by the UR because the UR provided housing, particularly for low-to middle-income individuals.Therefore, it is possible that the residents of public housing targeted in this study are not necessarily only from low-income households.Despite the aforementioned limitations, this study discussed important perspectives regarding the association between housing tenure and the risk of mortality.

Conclusion
In this study, we examined the risk of mortality among older Japanese residents living in private and public rented houses compared with that among those living in owner-occupied houses using 9-year follow-up data.We found that the risk of mortality was lower in those living in public rental houses than in those living in private rented houses and other types of rental houses.As aging leads to frailty, the housing environment may directly affect older individuals.Therefore, rental housing may also be important to consider during planned development, including the neighborhood.Investigating factors related to their living conditions among older populations is important to suggest healthy urban development.

Table 1 .
Baseline characteristics of older Japanese adults according to housing tenure (n = 44,007).

Table 2 .
Hazard ratios with 95% confidence intervals for the association of mortality with housing tenure among older Japanese adults (n = 44,007).